Black Hole Accretion Theoretical Limits And Observational Implications Dominikus Heinzeller...

Black Hole Accretion

Theoretical Limits And Observational Implications

Black Hole Accretion

Theoretical Limits And Observational Implications

Dominikus Heinzeller

Institute for Theoretical AstrophysicsCenter for Astronomy Heidelberg

Albert-Ueberle-Str. 2, 69120 Heidelberg

dh@ita.uni-heidelberg.de

Dominikus Heinzeller

Institute for Theoretical AstrophysicsCenter for Astronomy Heidelberg

Albert-Ueberle-Str. 2, 69120 Heidelberg

dh@ita.uni-heidelberg.de Credit: Michael Owen, John Blondin

slide 2D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Outline

1. Black hole accretion and the Eddington limit

2. Spectral energy distribution of super-Eddington flows

3. Conclusions

In collaboration with W.J. Duschl, S. Mineshige, K. Ohsuga

Supported by:

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 3D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Classical Eddington limit

• global upper limit for the luminosity of a star• spherical approximation often used in accretion discs:

rF

gF

• spherical symmetry

• homogeneous

• isotropic radiation

• no relativistic effects

• Thomson scattering

• no gas pressure

effT

r g E

4 + = 0 =

cGMF F L

38 8disc

erg1.2 10 2.6 10

s aM M

L m M m mM

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 4D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Contradictions

• cosmology: SMBHs in the early universeaccretion scenarios require super-Eddington accretion

• observation of super-Eddington luminosities: ULXs– sub-Eddington IMBHs?

too hot accretion disc problem– super-Eddington stellar mass BHs?

Current and previous work:• modification of global classical Eddington limit• local deviations

– leaky discs (Begelman 2002)– critical accretion discs (Fukue 2000, 2004)

E10L L

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 5D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Local Eddington limit in discs

• local Eddington limit for radial and vertical direction

• thin -discs (Shakura & Sunjaev 1973)• slim discs: advection (Abramowicz et al. 1980/1988)• Thomson scattering and interpolated opacities

(Gail, priv comm.)

• spherical symmetry

• homogeneous

• isotropic radiation

• no relativistic effects

• Thomson scattering

• no gas pressure

effT

??

rF

gF gFcF

r,oF r,iF

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 6D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Local Eddington limit in discs

• radial upper limit on vertical upper limit• • unimportant

for high (advection),otherwise crucial

• inner boundary?(here: torque-free)

• slim disc, :

while

M

Vertical Eddington limit

BH

7i

10

8.86 10 cm

=0.1

M M

s

crit E/M M

i/s s

1 2critM s

critM

3crit E/ 1 10M M

E/ 1 20L L

/ 1h s

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 7D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

SED of super-Eddington flows

• based on 2D RHD simulations (Ohsuga et al. 2005)– high accretion rates – energy transport via radiation and advection– consideration for photon trapping

• observer at inclination • parallel line of sight calculation of radiative

transfer– relativistic

effects– electron

scattering– -dependent

ff-absorption

0 /2

3E BH( 10 , 10 )M M M M

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 8D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

SED of super-Eddington flows

[erg/s]L

[eV]E

BlackbodyBlackbodytemperaturetemperaturefit to peak:fit to peak:

6

6

5

T(0)=

1.5 10 K

T( /4)

1.2 10 K

( /2)

9.4 10 K

T

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

slide 9D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

SED of super-Eddington flows

mild relativistic beaming mild relativistic beaming

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook

Blackbodytemperaturefit to peak:

6

6

5

T(0)=

1.5 10 K

T( /4)

1.2 10 K

( /2)

9.4 10 K

T

slide 10D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006

Conclusions

Black hole accretion:• classical Eddington-limit not applicable in

discs– depends on disc model– varies with distance from central object– inner disc region/boundary decisive

• bottle-neck in inner disc region• super-Eddington accretion and luminosities

Spectral energy distribution:• modelling of disc and its environment

necessary for interpretation of spectra• mild relativistic beaming

– increased photon number for small – enhanced average photon energy– high temperatures

Influence onBH growth?

Outflows, jets?

Evidencefor IMBH?

NGC 4261Credit:R.M. Elowitz

Outline

Black holeaccretion

SED of super-Eddington flows

Conclusionsand outlook